1. Field of the Invention
The present invention relates to a light-emitting device and a production method thereof.
2. Related Background Art
As a light-emitting device, two types of devices are known.
One is a device of current injection type, in which carrier (electron and holes) are injected into p-n junction and light is emitted by electron-hole recombination. This type of devices of a light emitting diode and a laser diode etc. is operated under relatively low voltages (<10V) and may be driven under DC condition.
Another is a device using electric field excitation, in which high electric field across stacked dielectric layer and light-emitting layer is used to accelerate electrons and excite the light-emitting layer. This type of device of inorganic EL etc. is operated under relatively high voltages and is driven under AC condition. A general inorganic EL has a double insulating structure with an electrode layer, a first insulating layer, a light-emitting layer, a second insulating layer, an electrode layer being stacked on a glass substrate.
These two types of device are different in their operation principles.
In this specification, the term “an electric field excitation light-emitting device” indicates the latter type of device using electric field excitation.
A flat panel display (FPD) having such a light-emitting device applied thereto has been attracting attention. As an FPD, an organic electroluminescence display (organic EL), an inorganic electroluminescence display (inorganic EL), a light-emitting diode display (LED display) are included.
A light-emitting diode can be driven with a low voltage and is excellent in stability, but requires high temperature process for crystal growth, and is therefore difficult to be formed on a glass substrate and a plastic substrate. Therefore, as a display, its range of application is limited.
An organic EL display can be driven with a low voltage and can be formed on a glass substrate or a plastic substrate, but has a problem in reliability and durability.
With regard to inorganic display, production of a large area display is comparatively easy, and high resistance to use environment can be expected, but the high drive voltage is currently problematic. Recently, in Japanese Patent Application Laid-Open No. 2002-280185, a technology on a thin film EL device with quantum size layers of alternately stacked films or a porous layer has been disclosed for improving light emission efficiency.